This invention relates to a thread retainer, otherwise commonly called a trim cover clip, which is made of a plastic substance and adapted to fasten a panel or some other similar object readily and detachably to a bolt having a male thread formed on the periphery thereof (hereinafter referred to as a "trim cover clip").
Attachment of this trim cover clip to a given bolt is accomplished by passing the bolt through the object until the leading end thereof protrudes from the object and pushing the trim cover clip in the axial direction onto the protruding end of the bolt. Detachment of the trim cover clip from the bolt is effected by turning the trim cover clip in the loosening direction of the thread in the same manner as a nut is unfastened from a bolt.
As can be seen from, for example, the prior art trim cover clip described in Japanese Utility Model Application Disclosure Sho 57(1982)-21815, the thread on the bolt is generally in the shape of a helical ridge so that when this bolt is passed through the object and a conventional trim cover clip is pushed in the axial direction onto the protruding leading end of the bolt to fasten the object to the bolt, the rack teeth of the trim cover clip come into engagement only in a limited part with the male thread on the bolt because these teeth have straight ridges running perpendicularly relative to the axial direction of the bolt and these ridges differ in shape from the helical ridge of the male thread on the bolt. Thus, the trim cover clip has an advantage that, during its attachment to the bolt, it can be pushed in with nominal force and, at the same time, suffers from a disadvantage that it can retain the object only weakly. When the conventional trim cover clip is used in attaching a finisher of an automobile trunk, for example, it will come loose on exposure to vibrations or other similar external impacts.